Retigabine (N-[2-amino-4-(4-fluorobenzylamino)phenyl]carbamic acid, ethyl ester] (U.S. Pat. No. 5,384,330) has been found to be an effective treatment of seizure disorders in children. Bialer, M. et al., Epilepsy Research 1999, 34, 1-41. Retigabine has also been found to be useful in treating pain, including neuropathic pain. Blackburn-Munro and Jensen, Eur. J. Pharmacol. 2003, 460, 109-116.
A form of epilepsy known as “benign familial neonatal convulsions” has been associated with mutations in the KCNQ2/3 channels. Biervert, C. et al., Science 1998, 27, 403-06; Singh, N. A. et al., Nat. Genet. 1998, 18, 25-29; Charlier, C. et al., Nat. Genet. 1998, 18, 53-55, Rogawski, Trends in Neurosciences 2000, 23, 393-398. Subsequent investigations have established that the primary site of retigabine action is the KCNQ2/3 channel. Wickenden, A. D. et al., Mol. Pharmacol. 2000, 58, 591-600; Main, M. J. et al., Mol. Pharmcol. 2000, 58, 253-62. Retigabine has been shown to increase the conductance of the channels at the resting membrane potential and to bind the activation gate of the KCNQ 2/3 channel. Wuttke, T. V. et al., Mol. Pharmacol. 2005, 67, 1009-1017.
The recognition of retigabine as a potassium channel modulator has prompted a search for other potassium channel modulators among compounds related to retigabine. Several such searches have been reported in the patent literature, most notably the following: WO 2004/058739; WO 2004/80950; WO 2004/82677; WO 2004/96767; WO 2005/087754; and WO 2006/029623.